Still being charged after 4 months

On the 15th Jan 15. I went into Telkom in the Penford shopping centre and asked for a mobile phone contract to be cancelled. Ref no. ***. Went in there again on Sat 30th April. Told to phone 10210. Try calling 10210. If you have a lot of time to sit listening to a sales jingle that just carries on repeating itself. Eventually you'll get an answer, they'll put you through to someone else and that's as far as it goes. Cut off. Tried this on three occasions and the same result. How long does it take? I'm still being billed.